#include<stdio.h>
int num(int n)
{
	if(n==2)
	return 1;
	else if(n==3)
	return 2;
	else
	{
	 return num(n-1)+num(n-2);
	}
}
int main()
{
	int m;
	while(scanf("%d",&m)!=EOF)
	{
		printf("%d\n",num(m));
	}
}
